Radio receiving system



E. B. LEWIS RADIO RECEIVING SYSTEM Filed Aug. 8, 1922 INVENTOR. Earle B Lazar/2s BY f A TTORNEY Patented Oct. 7, 1924.

UNITED STATES PATENT OFFICE.

HART-IE B. LEWIS, OF WATERBURY, CONNECTICTIT.

To all whom it may RADIO RECEIVING SYSTEM.

Application filed August 8, 1922. Serial No. 580,455.

Be it known that I EARLE B. LEWIS, a

citizen of the United county of New Haven,

of Waterbury,

tates, and a resident and State of Connecticut, have invented certain new and useful Improvements in Radio Receiving Systems, of which the following is a specification.

This invention relates plifying and detecti to a system for amng high frequency electromagnetic waves, and more particularly to a radio receiving system having an au lOIl detector.

One object of this invention is to provide means for permitting increased amplification of the received signals of sired locally gene a radio frequency to eliminate the undefeed-back currents originating intheiaudion and other parts of the circuit, by

erated' oscillations and from building up to A further object the ener ated oscillations,

er ally absorbing the oscillations.

A further object is suppressing such locally genthus preventing them an injurious degree. is to selectively absorb of such undesired locally generand to dissipate such in the form of'heat without materienergy of the desired to provide a receiving system of the above nature in which means are provided for tuning the energy absorbing means to the frequency of undesired waves.

A further object is to provide a device of the above nature which will be simple, easy to manipulate,

cheap to manufacture, comparatively fool-proof, and very efiicient and durable m use.

With these and other objects in view, there have been illustrate drawing several forms d on the accompanying in which the invention may be conveniently embodied in practice.

Fig. 1 represents one form therein.

Fig; 2 is a of the system shown in Fig.

modified form of thereto.

Fig. 3 is a diagra a diagrammatic view of havm diagrammatic view of a portion 1 showing a the invention app led mmatic view, similar to Fi 2, showing in perspective another form in wh ch the invention may Fig; 4a is a detailed be embodied. perspective view of the adjustable metal band of the modification shown in Fig. 8.

In the reception of radio waves it has been found that objectionable disturbing noises such as are due to variations in the batteries are less highly amplified when operating at radio-frequency than when operating at audio-frequency. For the above and other reasons it is desirable in wireless receiving sets to amplify as much as possible at radiofrequency.

Up to the present time, however, considerable difiiculty has been experienced with wireless receiving sets operating with radiofrequency particularly at short wavelengths. This difiiculty has been chiefly caused by the locally generated feed-bac oscillations in the grid circuit which interfered with the reception of the desired waves sent out by the transmitting or broadcasting station and often drowned them out altogether. These locally generated oscillations were caused principally by the capacity coupling which exists between the grid and plate of the audion. This caused the grid circuit to become unstable, especially when the successive stages of the set were transformer coupled.

According to the present invention, a radio-frequency receiving set has been provided, in which the above and other disadvantages have been largely, if not entirely, avoided. This has been accomplished by employing means external to the grid clrcuit and coupled to the inductance of said grid circuit adapted to be tuned into resonance with the undesired locally generated oscillations and which will absorb them selectively without afi'ecting the desired waves being received through the antenna.

Referring now to the drawings in which like reference numerals denote corresponding parts throughout the several views, the numeral 10 represents a receiving antenna of a wireless receiving system. The radio waves received by the antenna 10 pass through a variable condenser 11, an inductance coil 12, which is also preferably variable, a ground wire 13 to the ground 13.

The grid circuit of the first stage of amplification comprises a conducting wire 14, a grid 15, an incandescent filament 17, wire 18*, and wire 18 the latter being connected to the antenna circuit between the inductance coil and the ground wire-13. The

grid 15, the filament l7, and plate 18 are mounted as usual in an evacuated audion tube l6.

In order to connect plification to the second stage, of the audion 16 is connected to a primary coil 19 of a. transformer 20. The primary coil 19 is inductively coupled to the secondary coil 21 which is located in the grid circuit of the second stage.

The amplified oscillations from the second stage are next rectified and convertedto audio-frequency oscillations in the third stage or detector of the set. The plate 24 of the second stage is connected to a primary coil 25 of a second transformer 26, the primary coil 25 being inductively coupled to a secondary coil 27 in the third stage. A rid condenser 28 is employed in this stage between the secondary coil 27 and the grid 29.

The audio-frequency oscillations from the third stage or detector 30 are converted into audible sound waves by means of a telephone receiver 30 which is located between the plate 31'- and the B battery of the detector plate circuit. It will be understood of course that a loud speaker may be substituted for the telephone receiver within the spirit of the invention.

As clearly shown in Fig. 1, the audion plates 18 and 24. of the radio-frequency stages are connected to a bus-bar 31 leading to the positive terminal of the B battery shown at the right of the figure. Each of the audion filaments 17, 23, and 31 are connected to the busbars 32 and 33 leading to the positive and negative terminals respectively of the A battery, adjustable rheostats 34, 35 and 36 being provided to enable the temperature of the filaments to be separately controlled.

The device for selectively absorbing the the first stage of amthe plate 18 energy of the undesired oscillations of the til grid circuit will next be described. This device, as herein disclosed, comprises an exterior closed circuit inductively. coupled with the induction coil 12. In the form shown in Fig. 1, an inductance coil 37 is provided and is shunmd by a variable condenser 38, by means of which the closedcircuit may be tuned into resonance with the undesired oscillations of the grid circuit of the first stage. lln the modified form of energy absorbing device illustrated in Fig. 2, a rheostat 39 is employed as the tuning means, instead of t e variable condenser 38 illustrated in 5n the operation of the systems illustrated in Fig. 1 and Fig. 2, the inductive closed circuit will first be tuned into resonance with the locally generated oscillations of the grid circuit. lhe grid circuit will next be tuned into resonance with the desired waves being sent out by the transmitting station. This release may be accomplished by suitably adjusting the variable condenser 11.

When the exterior inductive closed circuit has been properly adjusted it will act as an absorbing device for the undesired vibrations of the grid circuit, said vibrations being dissipated as heat in the exterior closed circuit.

In Figs. 3 and l, a still further form of energy absorbing device is illustrated. In this form, a circular closed metal band 10 is rotatably mounted within a ring l-l formed on the end of the coil 12. The band 40 is provided with a shaft 42 whose axis 's at right angles to the axis of the coil 12. The shaft 42 has a pair of bearing portions 43 and 44 adapted to fit within suitable apertures inthe ring 41, and is provided with a knob 45 whereby the band 40 may be easily rotated to vary the inductive efiect. lln practice the dimensions and shape of the band 40 will be chosen so that it will be in resonance with the undesired oscillations of the grid circuit, and it will absorb such oscillations in the same manner as the devices illustrated in Figs. land 2.

One important advantage of the present invention is that theabsorption of the undesired locally generated energy will be accomplished without materially diminishing the intensity of the received oscillations.

Another advantage is that the absorption of such energy will prevent the undesired oscillations from building up to an injurious degree, even when the successive stages of the set are transformer coupled, and con sequently a higher degree of amplification may be secured without maln'ng the tubes unstable.

While the means for absorbing undesired oscillations has been illustrated only in the first stage of a radio-frequency system, it will be understood that it may also be a plied to other stages of this system or in any other systems in which it is desired to absorb the high-frequency oscillations.

While there have been disclosed in this specification several forms in which the invention may be embodied. it is to be understood that these forms are shown for the purpose of illustration only, and that the invention is not to be limited to the specific disclosures, but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and em bodiments coming within the scope oi. the following claims.

Having thus fully described the invention. what is claimed as new, and for which it is desired to secure Letters Patent, is:

l. lln an audion radio receiving system, a grad circuit, an. audion tube, an absorbing device for the undesired oscillations fed back into said grid circuit from said audion tube comprising an inductance coil in said grid ill? circuit, said coil including an outer stationary metallic ring in series therewith, an inner closed ring located within said outer ring and mounted on an axis which is in the plane of said outer ring, said inner ring being adapted to be rotated on its axis whereby the energy of said oscillations will be selectively absorbed by induction and dissipated as heat.

2. In an audion radio receiving system, a grid circuit, an audion tube, an absorbin device for the undesired oscillations fed bac into said grid circuit from said eudion tube comprising an inductance coil in said grid circuit,-said coil including an outer station- 1 EARLE B. LEWIS.

I have aifixed my 25 signature to this specification. 

